The invention pertains to endotracheal-device placement in a patient requiring assured airway access, for breathing or anaesthetic purposes, for example, after the patient has lost consciousness with resulting compromise to the air passages, which can be life-threatening, if the airway access is not quickly and assuredly accomplished.
Endotracheal intubation using a laryngoscope is a relatively skilled procedure and inevitably involves distortion of the anatomy in order to bring the glottis into the line of sight. In addition, an endotracheal tube (ET) is designed for ease of passage when the anatomy is thus distorted; thus, curvature of the ET does not correspond with the contours of the relaxed anatomy of the patient's upper airway. Because it is not always possible or desirable to distort the anatomy, the so-called "difficult" airway remains an important cause of mortality and morbidity in anaesthesia, in spite of a plethora of intubating aids and difficult-airway algorithms.
The laryngeal mask (LMA) has found a place in this arena, but suffers from the disadvantage that its airway tube is too long and narrow to act as an acceptable conduit for intubation, in that it cannot be removed easily from the ET, once intubation has been accomplished. In addition, the mask-aperture bars (MAB) of an LMA may obstruct or deflect ET passage. Nevertheless, the LMA has the advantage that ventilation can usually be maintained, whether or not the patient can be intubated. Examples of LMA devices in prior-art patents are to be found in U.S. Pat. Nos. 4,509,514; 4,995,388; 5,241,956; 5,303,697*, 5,355,879; 5,477,851* (now Reissue patent Re. 35,531*); and also in pending U.S. application Ser. No. 08/826,563, filed Apr. 4, 1997*. Of these patent disclosures, those just identified by asterisk (*) deal in one way or another with various structural improvements to facilitate use of an LMA as an aid to intubation.
U.S. Pat. No. 5,303,697 discloses use of an intubating LMA featuring a rigid stainless-steel airway tube with an inflatable mask at its distal end. The point of the invention was to adopt as thin as possible tube-wall thickness, for purposes of accommodating a range of ET diameters, and to enable manipulation of the placement of the distal mask. The two embodiments of this patent show curvature of the rigid tube to be of differing arcuate extent, namely, either (i) a right angle or (ii) somewhat less than a right angle; and my experience in working with either of these configurations is that distortion of the anatomy was needed, e.g., by the anesthesiologist lifting the patient's neck and extending the head to seek an accommodating non-neutral* variation of spine curvature in the neck region, in order to achieve suitable conditions for LMA placement and intubation through the LMA. Such manoeuvering has at least the disadvantages of (a) requiring full mobility of the bones of the neck, and (b) inviting neurological damage if the patient has sustained a neck injury.